JSTests/wasm/function-tests/loop-sum.js

import Builder from '../Builder.js'
import * as assert from '../assert.js'

const b = new Builder();
b.Type().End()
    .Function().End()
    .Export()
        .Function("loop")
    .End()
    .Code()
    .Function("loop", { params: ["i32"], ret: "i32" }, ["i32"])
    .I32Const(0)
    .SetLocal(1)
    .Loop("void")
    .Block("void", b =>
           b.GetLocal(0)
           .I32Const(0)
           .I32Eq()
           .BrIf(0)
           .GetLocal(0)
           .GetLocal(1)
           .I32Add()
           .SetLocal(1)
           .GetLocal(0)
           .I32Const(1)
           .I32Sub()
           .SetLocal(0)
           .Br(1)
          )
    .End()
    .GetLocal(1)
    .Return()
    .End()
    .End()

const bin = b.WebAssembly().get();
const module = new WebAssembly.Module(bin);
const instance = new WebAssembly.Instance(module);

assert.eq(0, instance.exports.loop(0));
assert.eq(1, instance.exports.loop(1));
assert.eq(3, instance.exports.loop(2));
assert.eq(5050, instance.exports.loop(100));